Acoustic neuroma is an uncommon, noncancerous (benign) and usually slow-growing tumor that develops on the main nerve leading from your inner ear to your brain. Because branches of this nerve directly influence your balance and hearing, pressure from an acoustic neuroma can cause hearing loss, ringing in your ear and unsteadiness.

Also known as vestibular schwannoma, acoustic neuroma usually grows slowly or not at all. However, in a few cases, it may grow rapidly and become large enough to press against the brain and interfere with vital functions.

The signs and symptoms of acoustic neuroma develop from direct effects on the main nerve or from the tumor pressing on adjacent nerves, nearby blood vessels or brain structures.

As the tumor grows, it may be more likely to cause signs and symptoms, although tumor size doesn't always determine effects. It's possible for a small tumor to cause significant signs and symptoms.

You may experience signs and symptoms such as:

Hearing loss, usually gradual — although in some cases sudden — and occurring on only one side or more pronounced on one side

Ringing (tinnitus) in the affected ear

Unsteadiness, loss of balance

Dizziness (vertigo)

Facial numbness and very rarely, weakness

In rare cases, an acoustic neuroma may grow large enough to compress the brainstem and threaten your life.

When to see your doctor

See your doctor if you notice hearing loss in one ear, ringing in your ear or trouble with your balance. Early diagnosis of an acoustic neuroma may help keep the tumor from growing large enough to cause serious consequences, such as total hearing loss or a life-threatening buildup of fluid within your skull.

The cause of acoustic neuromas — tumors on the main balance nerves leading from your inner ear to your brain (eighth cranial nerve) — appears to be a malfunctioning gene on chromosome 22. Normally, this gene produces a protein that helps control the growth of Schwann cells covering the nerves. What makes this gene malfunction isn't clear, and currently there are no known risk factors for getting an acoustic neuroma.

Scientists do know the faulty gene is inherited in neurofibromatosis type 2, a rare disorder that usually involves the growth of tumors on balance nerves on both sides of your head (bilateral vestibular schwannomas).

The only known risk factor for acoustic neuroma is having a parent with the rare genetic disorder neurofibromatosis type 2, but this accounts for only a small number of cases. A hallmark characteristic of neurofibromatosis type 2 is the development of benign tumors on the balance nerves on both sides of your head, as well as on other nerves.

Neurofibromatosis type 2 (NF2) is known as an autosomal dominant disorder, meaning that the mutation can be passed on by just one parent (dominant gene). Each child of an affected parent has a 50-50 chance of inheriting it.

Another possible risk factor that may be associated with acoustic neuroma includes childhood exposure to low-dose radiation of the head and neck.

An acoustic neuroma may cause a variety of permanent complications, including:

Hearing loss

Facial numbness and weakness

Difficulties with balance

Ringing in the ear

Large tumors may press on your brainstem, preventing the normal flow of fluid between your brain and spinal cord (cerebrospinal fluid). In this case, fluid can build up in your head (hydrocephalus), increasing the pressure inside your skull.

You're likely to start by seeing your family doctor or a general practitioner. Your doctor may then refer you to a doctor trained in ear, nose and throat conditions (otorhinolaryngologist) or a doctor trained in brain and nervous system surgery (neurosurgeon).

Because there's often a lot to talk about during your appointment, it's a good idea to be well-prepared. Here's some information to help you get ready for your appointment, and what to expect from your doctor.

What you can do

Write down any symptoms you're experiencing, including any that may seem unrelated to the reason for which you scheduled the appointment.

Make a list of all medications, vitamins or supplements that you're taking.

Ask a family member or friend to join you, if possible. Sometimes it can be difficult to remember all the information provided to you during an appointment. Someone who accompanies you may remember something that you missed or forgot.

Write down questions to ask your doctor.

Preparing a list of questions will help you make the most of your time with your doctor. For acoustic neuroma, some basic questions to ask your doctor include:

What is likely causing my symptoms?

Are there any other possible causes for my symptoms?

What kinds of tests do I need?

What treatment options are available?

Which one do you recommend for me?

What is the likelihood of side effects from each treatment option?

What happens if I do nothing?

Are there any brochures or other printed material that I can take home with me? What websites do you recommend visiting?

In addition to the questions that you've prepared to ask your doctor, don't hesitate to ask questions during your appointment.

What to expect from your doctor

Your doctor is likely to ask you a number of questions. Being ready to answer them may reserve time to go over any points you want to spend more time on. Your doctor may ask:

When did you first begin experiencing symptoms?

Have your symptoms been continuous or occasional?

How severe are your symptoms?

Do you have any family members with an acoustic neuroma?

At its current level, do you feel the hearing in the affected ear is useful to you in any way? For example, can you use that ear on the telephone, or does that ear help you tell where sound is coming from?

Do you have regular headaches currently or have you had them in the past?

Because signs and symptoms of acoustic neuroma are likely to develop gradually and because symptoms such as hearing loss can be indicators of other middle and inner ear problems, it may be difficult for your doctor to detect the tumor in its early stages.

After asking questions about your symptoms, your doctor will conduct an ear exam. Your doctor may order the following tests:

Hearing test (audiometry). In this test, conducted by a hearing specialist (audiologist), you hear sounds directed to one ear at a time. The audiologist presents a range of sounds of various tones and asks you to indicate each time you hear the sound. Each tone is repeated at faint levels to find out when you can barely hear.

The audiologist may also present various words to determine your hearing ability.

Scans. Contrasted magnetic resonance imaging (MRI) or computerized tomography (CT) scans of your head can provide images that confirm the presence of an acoustic neuroma.

Your acoustic neuroma treatment may vary, depending on the size and growth of the acoustic neuroma and if you're experiencing symptoms. To treat acoustic neuroma, your doctor may suggest several possible treatments.

Monitoring

If you have a small acoustic neuroma that isn't growing or is growing slowly and causes few or no signs or symptoms, you and your doctor may decide to monitor it, especially if you're an older adult or otherwise not a good candidate for treatment.

Your doctor may recommend that you have regular imaging and hearing tests, usually every six to 12 months, to determine whether the tumor is growing and how quickly. If the scans show the tumor is growing or if the tumor causes progressive symptoms or other difficulties, you may need to undergo treatment.

Stereotactic radiosurgery

Your doctor may recommend stereotactic radiosurgery (ster-e-oh-TAK-tik ray-dee-oh-SUR-jur-e) if you have an acoustic neuroma. Some very large tumors can't be treated with stereotactic radiosurgery.

The goal of stereotactic radiosurgery is to stop the growth of a tumor, preserve the facial nerve's function and possibly preserve hearing. However, a study has found that many people gradually lose their hearing within 10 years after stereotactic radiosurgery.

In stereotactic radiosurgery, such as Gamma Knife radiosurgery, doctors deliver radiation precisely to a tumor without making an incision. The doctor attaches a lightweight head frame to your scalp, which has been numbed, to keep your head still during the procedure. Using imaging scans, your doctor pinpoints the tumor and then plots where to direct the radiation beams.

It may take weeks, months or years before the effects of radiosurgery become evident. Your doctor will monitor your progress with follow-up imaging studies and hearing tests.

Risks of radiosurgery include hearing loss, ringing in the ear, facial weakness, facial numbness, balance problems and treatment failure (continued tumor growth). Very rarely, the radiation could cause a cancer in the treated area in the future.

Surgical removal

You may need surgery to remove an acoustic neuroma. Your surgeon may use one of several techniques for removing an acoustic neuroma, depending on the size of your tumor, preoperative hearing status and other factors. The goal of surgery is to remove the tumor, preserve the facial nerve to prevent facial paralysis and preserve hearing when possible.

Surgery for an acoustic neuroma is performed during general anesthesia and involves removing the tumor through the inner ear or through a window in your skull. The entire tumor may not be able to be completely removed in some cases. For example, if the tumor is too close to important parts of the brain or the facial nerve.

Surgery can create complications, including worsening of symptoms, if certain nerve or cranial structures are affected during the operation. These risks are often based on the size of the tumor and the surgical approach used.

Complications may include:

Leakage of cerebrospinal fluid through the wound

Hearing loss

Facial weakness

Facial numbness

Ringing in the ear

Balance problems

Persistent headache

Infection of the cerebrospinal fluid (meningitis)

Stroke or brain bleeding

Dealing with the possibility of hearing loss and facial paralysis and deciding which treatment would be best for you can be quite stressful. Here are some suggestions you may find helpful:

Educate yourself about acoustic neuroma. The more you know, the better prepared you'll be to make good choices about treatment. Besides talking to your doctor and your audiologist, you may want to talk to a counselor or social worker. Or you may find it helpful to talk to other people who've had an acoustic neuroma and learn more about their experiences during and after treatment.

Maintain a strong support system. Family and friends can help you as you go through this difficult time. Sometimes, though, you may find the concern and understanding of other people with acoustic neuroma especially comforting.

Your doctor or a social worker may be able to put you in touch with a support group. Or you may find an in-person or online support group through the Acoustic Neuroma Association.

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